The chemical formula of mineral Howlite is indicated by Ca2B5SiO9(OH)5 or Calcium Boro-silicate Hydroxide. Howlite is classified as a Silicate mineral as well as a Carbonate mineral. This is so because Howlite is actually very confusing to distinguish and classify. When based on its chemical formula, it is best classified as a Silicate mineral. But because of the five borons to only one silicon character and formation that it possesses, Howlite is also in line with other borate minerals like ulexite, kernite, colemite, and borax, all of which are classified under the Carbonates mineral class. Howlite was named after Henry How (1828-1879), a Canadian chemist, geologist, and mineralogist, of Nova Scotia. It is him who first discovered the mineral species Howlite. The first Howlite specimen was found at the Brookville, Nova Scotia, Canada in the year 1868. Howlite is known to crystallize in the monoclinic system of crystal formation. In optical mineralogy, the monoclinic system of crystal formation comprises crystals having three axes of unequal lengths. Two of which are usually found in a position that is oblique or not perpendicular to one another. However, both of which are commonly found perpendicular to the third axis.
Howlite is used as a source of the element boron. Howlite stone is also used as an ornamental stone and often carved as bead figurines and polished cabochons that are usually very interesting when viewed under gemological microscopes. Sometimes, Howlite crystals are used as substitute for turquoise. Howlites can be also used as mineral specimens for they can be also found exhibiting interesting microscope appearance when viewed under petrographic polarizing microscope.
Howlite is most commonly found white with gray to black streaks and is also capable of exhibiting splendid microscope images when viewed under polarizing light microscopes for mineralogists. Howlite crystals are usually found with web-like markings and blotches when the mineral is closely evaluated with the aid of petrographic polarizing light microscope used in optical mineralogy. Howlite crystals is most commonly found showing a dull to sub-vitreous or porcelaneous and earthy luster when viewed in reflected light of polarized microscope for mineralogists. Howlite can be also found showing an absent cleavage when it is closely evaluated with the aid of polarizing microscope for mineralogists Howlite is also usually found exhibiting a conchoidal to uneven fracture when viewed closely under a geological polarizing microscope used in optical mineralogy. The specific gravity measure of the mineral usually gives an approximate value ranging from 2.5 grams per cubic centimeters to 2.6 grams per cubic centimeters, which is considered slightly below average. The hardness measure of the mineral Howlite when it is evaluated using the Mohs scale method is usually 3.5. Howlite is most commonly found leaving a white streak when specimen sample is rubbed on a white porcelain streak plate.
Most Howlite mineral crystals are found opaque to translucent in appearance. The crystal habits of mineral Howlite as described in optical mineralogy usually include cauliflower-like nodules and compact and it sometimes includes micaceous masses that are splendidly exhibited under polarizing microscopes for mineralogists. Howlite crystals are very rare. But minute or 1mm size tabular and six-sided crystals of Howlite are sometimes aggregated into rosettes and they can be splendidly exhibited under a petrographic polarizing light microscope used in optical mineralogy. Some nodules are sometimes found having crystal faces on their surfaces when closely examined with the aid of petrographic polarizing microscope and these specimens are mostly from the Nova Scotia.
Howlite is most commonly found showing a moderate surface relief when viewed under several adjustments on the aperture diaphragm of the polarizing microscopes for mineralogists. Howlite is most commonly found showing a biaxial negative figure when closely evaluated between crossed nicols of polarizing light microscopes used in optical mineralogy. The refractive index of the mineral Howlite is most commonly found ranging from 1.583 to 1.600. It has no dispersion display when viewed under polarized microscopes. The maximum birefringence of Howlite under polarized microscope is commonly found 0.017. Howlite mineral specimens are sometimes found fluoresces a blue, yellowish white or off-white color under short wave ultra violet light. Howlite also dissolves in hydrochloric acid solution without bubbling. There is no specific data found on the toxicity and health dangers for mineral Howlite. However, the specimens of this mineral species should be treated with great care and use of sensible precaution is advised upon handling them.
Mineral Howlite is commonly associated with ulexite, colemanite, gypsum, clays, and anhydrite. The best field indicators of mineral Howlite usually include its nodular character, solubility in HCl, lack of cleavage, color, softness, and luster. Mineral Howlite can be found in the continental evaporite deposits with other borate and evaporate minerals. Howlite commonly forms in nodules, which appear like the heads of cauliflower. Crystal faces on the nodules are very rare in occurrence. Another additional character of these nodules is the vein of black web-like streaks that are often found interlaced throughout the nodules. These veins are artistically painted with scenes and designs. Howlite is also a secondary mineral in arid environments. Howlite mineral specimens notably occurs at several localities including some borate deposits in California, USA as well some other areas like the Sterling Borax Mine, Tick Canyon and Lang, Los Angeles County as well as the Gower Gulch, Inyo County and Dagget, San Bernardino County. It can be also found at the Latonville Quarry, Brookville, Windsor and Iona in Nova Scotia as well as at the Newfoundland and the New Brunswick in Canada.
